Adjustable backrest

ABSTRACT

An adjustable backrest for supporting a human back comprising a spine member; a lumbar support member projecting from the spine member; a back pad resting on the lumbar support member for supporting the human back; means for adjusting curvature of the lumbar support member and means for adjusting curvature of different portions of the back pad to accommodate different shapes of the human back; means for providing side-to-side mobility of the back pad to accommodate twisting movement of the human back.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of application Ser. No. 08/102,284 filedAug. 5, 1993 now U.S. Pat. No. 5,344,211.

FIELD OF THE INVENTION

The present invention relates in general to backrests, and moreparticularly an adjustable backrest having independent adjustment oflumbar and upper back height and curvature, as well as overall heightadjustment to fit different size patients.

BACKGROUND OF THE INVENTION

Adjustable backrests or supports are well known in the art. U.S. Pat.No. 5,112,106 (Asbjornsen et al) discloses a backrest comprising acentral spine or rail to which a lumbar support cushion and head cushionare connected via a sliding element. The sliding element is connected tothe rail or spine via a ratchet-like connection. The '106 Patent is ofinterest for teaching the concept of height adjustable lumbar supportwhere the adjusting means is connected to a spine for sliding engagementtherewith.

U.S. Pat. No. 2,756,809 (Endresen) discloses a back support comprising ametal sheet with adjustable lumbar and upper-back portions. A screwadjusts the concavity of the upper-back portion while a further screwadjusts the convexity of the lumbar support portion. A pair of crossbars are provided for supporting and securing the lumbar and upper backportions of the sheet to the backrest. The two adjustment screws aremounted on a pair of sliding plates to provide vertical adjustment ofthe lumbar support area and the upper-back support area. Accordingly,this patent is of interest for teaching independent height and curvatureadjustment of the lumbar support and upper-back support portions of abackrest.

Additional references are known which pertain to adjustable back supportor backrests, as follows: U.S. Pat. Nos. 2,843,195; 3,241,879;3,762,769; 4,153,293; 4,452,458; 4,541,670; 4,601,514; 4,632,454;4,722,569; 4,909,568; 4,915,448; 4,968,093; 5,026,116; and 5,197,780, aswell international patent application No. PCT/AU91/00487 (BackCare andSeating Pty. Ltd.).

While the known prior art backrests disclose the provision of lumbar andupper-back support members with independently adjustable curvature andpositioning, none of the known prior art teaches the combinations ofheight adjustment, lumbar height and curvature adjustment, upper-backcurvature and position adjustment and side-to-side mobility. Theprovision of these features in a backrest is important to ensure properfitting of the backrest for adult bodies of different height and shapes.Furthermore, human beings tend not to be static but like to move or"fine tune" their sitting positions. The known prior art backrests donot provide adequate side-to-side mobility for such movement. Nor dothey allow for the convenient minor adjustment of support. In addition,the known prior art back supports are generally bulky or heavy to carryand occupy excessive space at the bottom portions thereof, therebyleaving very little room to sit on a chair.

SUMMARY OF THE INVENTION

According to the present invention, a backrest is provided in whichlumbar height and curvature adjustment are provided along with overallheight adjustment to fit different sized persons. Additionally,upper-back curvature and height adjustment are provided along with sideadjustment to suit each half side of the human back (i.e. foraccommodating different torso shapes). Also, side-to-side mobility isprovided to accommodate twisting movements of the human back which arecommon when a person is sitting (e.g. turning to reach something, or"fine tuning" of one's sitting position). Furthermore, according to thebackrest of the present invention a slight hollow is provided just abovethe base of the backrest to allow for curvature and space so that thebackrest does not occupy excessive space on a chair.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the backrest according to the presentinvention resting on a chair;

FIG. 2 is a cross section along lines II--II of FIG. 1;

FIG. 3 is a rear perspective view of the backrest according to thepresent invention;

FIGS. 4A and 4B are cross sectional views along the lines IV--IV of FIG.3 showing curvature adjustment of the lumbar support and upper backsupport of the backrest according to the present invention;

FIG. 5 is a front perspective view of the backrest according to thepresent invention with the back pad shown in phantom;

FIG. 6 an exploded front perspective view of the structural details ofthe backrest according to the present invention;

FIG. 7 is a perspective view of the backrest according to an alternativeembodiment of the present invention;

FIG. 8 is a rear perspective view, partly broken, of the backrestaccording to the alternative embodiment;

FIGS. 9A and 9B are cross sectional views along the lines IX--IX of FIG.8 showing curvature adjustment of the lumbar support and upper backsupport of the backrest according to the alternative embodiment;

FIG. 10 is a front perspective view of the backrest according to thealternative embodiment with the back pad shown in phantom; and

FIG. 11 is an exploded front perspective view of the structural detailsof the backrest according to the alternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning first to FIG. 1, the backrest of the present invention is showncomprising a generally triangular upper portion 1 and base portion 3resting on the seat of chair C. The triangular profile of upper portion1 facilitates side-to-side movement of a person using the backrest ofthe present invention. Also, the hollow portion between the portion 1and base portion 3 ensures that the backrest does not occupy excessivespace on the chair C.

Turning to the remaining FIGS. 2-6, the details of construction of thepreferred embodiment are illustrated. A spine 5, preferably of rigidaluminum, forms a central support portion of the backrest to which allother parts are attached. The spine 5 is fabricated to form a pair ofcylindrical channels 7 and 9 intermediate a groove 11. As will bediscussed in greater detail below, the spine 5 also includes a pluralityof slots and apertures for the connection and securing of the variousother parts.

A lumbar spring 13 has a projection 15 from a bottom end thereof whichis shaped so as to be received in a clip 17. The clip 17 is riveted intospine 5 via a rivet 19 or other suitable attachment means. Thus, thelower portion of lumbar spring 13 is rigidly connected to the spine 5.As will be discussed in greater detail below, an upper portion of thelumbar spring 13 contains a projection 21 which is adapted to slidewithin the groove 11 of the spine 5 to permit curvature adjustment ofthe lumbar spring 13.

A cross bar 23 is provided in the form of a flat piece of metal (e.g.steel) which in conjunction with the back pad 49 and lateral adjustmentstraps 51 and 53 (discussed below), contributes to side-to-side lateralsupport of the backrest. The cross bar 23 is attached to back pad 4a asdiscussed in greater detail below.

An adjustment strap 25 is provided with a clip 27 at one looped endthereof and a D-ring 29 at an opposite looped end thereof. The end withclip 27 is dimensioned to pass through an aperture 31 in the spine of 5as shown by the arrow in FIG. 6 such that the clip 27 may be secured toone of a plurality of slots 33 in the spine.

At the other end, the projection 21 of lumbar spring 13 is dimensionedto pass through D-ring 29 which remains on an opposite side of the spine5 from the clip 27 and is adapted to slide within the groove 11 thereof,as will be discussed in greater detail below.

According to an important aspect of the present invention, curvature ofthe lumbar spring 13 may be adjusted. Turning to FIGS. 4A and 4B, themanner of such adjustment is shown. In order to adjust the curvature ofspring 13, the clip 27 at the lower looped end of adjustment strap 25 isremoved from one of the slots 33 in spine 5 by pulling downwardlyagainst the tension of the spring 13 and releasing. Pulling of theadjustment strap 25 is facilitated by the loop 39 through which a fingermay be inserted. Once the clip 27 has been removed from the slot 33, asshown in FIG. 4B, curvature of the lumbar spring 13 may be decreased byallowing the adjustment strap 25 to be released upwardly toward the slot31 in spine 5. Alternatively, as shown in FIG. 4B, by pulling downwardlyon the adjustment strap 25, D-ring 29 pulls the projection 21 of lumbarspring 13 downwardly, thereby increasing the curvature of the spring inthe direction of the arrow.

An upper back spring 35 is provided having a slot 37 at a base portionthereof through which the projection 21 is adapted to be inserted (shownbest in FIGS. 5 and 6).

According to another important aspect of the invention, independentcurvature of the upper back spring 35 is also provided. A cylindricaltube 41 is capped on both sides via end caps 43, and is secured to thespine 5 via retention spring 45 which slides within the groove 11 andwhich is riveted to the upper back support tube 41 via rivet 47. Bypushing the tube 41 downwardly in the direction of the arrow in FIG. 4B,the upper back spring 35 assumes a greater degree of curvature (ie.concavity), as illustrated. In addition, the tube 41 may be easilyremoved in order to remove any curvature in the upper back spring 35.

A back pad 49 (FIG. 5) is provided with a pair of adjustment straps 51and 53 having hook and loop type fasteners thereon (i.e. velcro™) whichpass through a pair of slots 55 in the back pad 49 in order to adjustthe contour of back pad 49, as discussed in greater detail below. Eachof these straps is independently and individually adjustable of eachother allowing for precise side-to-side contouring.

The back pad 49 is connected to the upper spring 35 via a screw (notshown) or other attachment means passing through holes 57 and 59 (FIG.5). The back pad 49 is connected at a lower end thereof to a furtherretention spring 61 which slides within the groove 11. Back pad 49 isconnected to retention spring 61 via rivet 63 and hole 65 (FIG. 5).Thus, the back pad 49 is free to move upwardly and downwardly relativeto the spine 5 as a result of the sliding connection of retention spring61, upper back support spring 35 and cross bar 23 which is mounted tolumbar support spring 13.

As shown in FIGS. 1, 2 and 3, the back pad 49 is covered by a suitablefabric and foam cover 67 which provides a soft cushion for receiving thehuman back, the overall vertical profile of the cushion being dictatedby the curvatures of the lumbar support spring 13, upper back supportspring 35 and back pad curvature adjustment straps 51 and 53. As shownin FIG. 3, the back pad adjustment straps are attached via rivets orother suitable means to the back pad 49 via apertures 69, and extendthrough the rear of the fabric and foam cushion 67 via slots 71 and 73for connection rearwardly of the backrest to suitable hook-and-loop(i.e. Velcro™) fasteners 75 (see FIGS. 2 and 3). By pulling on theadjustment straps 51 and 53, the curvature of the back pad 49 and hencethe cushion 67 covering it, is caused to increase in the direction ofthe arrows shown in FIG. 3.

The back pad 49 is of generally deltoid shape and preferably fabricatedfrom plastic panel to allow free shoulder rotation and upper backtwisting.

The base portion 3 of the backrest includes a wire foot 77 covered withself skinning plastic foam 79. As shown in FIG. 6, cylindrical endportions of the wire foot 77 are adapted to slide within the cylindricalholes 7 and 9 (FIG. 2) of the spine 5 for upward and downward slidingmovement of the wire foot 77 as shown with reference to the arrows atthe bottom of FIG. 3. The wire foot 77 is secured in place relative tospine 5, after height adjustment, by means of a pair of screws 80 andcorresponding nuts 82.

A self skinning wire head 81 is inserted into the tubular grooves 7 and9 at the top of spine 5 to provide a pleasing aesthetic finish and anintegral carrying handle. The wire head 81 is secured within spine 5 viaa pair of screws 83 and corresponding nuts 85 which cause the grooves 7and 9 to close around the wire head 81. In order to assemble thebackrest according to the present invention, cross bar 23 is firstattached to the lumbar spring 13 using very high bond tape, or othersuitable material, as discussed above. The Velcro™ adjustment straps 51and 53 and the cross bar 23 are then riveted to back pad 49. Lumbarspring 13 and upper back spring 35 are hooked together as shown in FIG.6, and the upper back spring 35 is riveted to the back pad 49 asdiscussed with reference to FIG. 5. The retention spring 61 is rivetedto the back pad 49 through hole 65 (FIG. 5).

Clip 27 is then riveted to the lumbar adjustment strap 25, forming aloop 39.

Wire foot 77 is inserted into the spine 5 and fastened into place withmachine screws 80 and nuts 82. Loop 29 is hooked to the lumbar spring 13and this assembly is then made to slide into the channel 11 in the spine5. The lumbar adjustment strap 25 is then inserted through the D-shapedloop and riveted to the end thereof, and the opposite looped end 39 ofthe strap 25 is pushed through slot 31 at the back of the spine 5. Theassembly comprising lumbar spring 13, D-shaped loop 29 and upper backspring 35 is pulled downwardly to allow the retention spring 61 to slideinto the spine 5 from the bottom. The assembly is then pulled back upand the bottom end 15 of the lumbar spring 13 is hooked into clip 17.

Next, the retention spring 45 is riveted to the upper back support tube41. End caps 43 are inserted into the sides of the upper back supporttube 41, and the assembly comprising the upper back support spring 35and retention spring 45 are inserted into the channel 11 of spine 5 fromthe top.

The wire head 81 is then inserted into the top of the spine 5, thefabric and foam cover 67 is placed over the back pad 49, and the variousstraps 25, 51 and 53 are adjusted for personal setting.

An alternative embodiment of the invention is illustrated in FIGS. 7-11.The alternative embodiment is similar in many respects to the embodimentshown in FIGS. 1-6. Where the features are identical, no additionaldescription is provided herein, and the same reference numerals havebeen used in FIGS. 1-6 and FIGS. 7-11 to identify like components.

In the alternative embodiment, the wire head 81A is provided with arubberized sleeve for enveloping the protruding top portion of the wirehead, rather than completely encapsulating the wire head 81 as in theembodiment in FIG. 1-6.

The spine 5 is of slightly modified design in that cylindrical channelsinto which the ends of the wire head 81A are inserted, have been createdin the spine, thereby eliminating the requirement for screws 83 and nuts85 (FIGS. 1-6).

In the alternative embodiment, spring 35A has been shortened and thematerial from which it is fabricated (eg. plastic) is strengthenedrelative to the spring 35 in the embodiment of FIGS. 1-6, so as toprovide the same level of resiliency as in the embodiment of FIGS. 1-6.

The back pad 49 is connected to anchoring spring 35A via a pair of nutsand bolts (FIG. 10) which pass through a pair of holes 59A in back pad49 and a pair of holes 57A in spring 35A, thereby replacing the singleholes 57 and 59 in the embodiment of FIGS. 1-6.

The method of securing the lumbar spring 13 for a predetermined amountof curvature is substantially modified in the embodiment of FIGS. 7-11,resulting in the elimination of slots 33. In the alternative embodiment,one end of a first adjustment strap 25 is connected to the spine 5 via arivet 28 and the other end is connected to a friction buckle 33A. Thestrap 25 passes upwardly from buckle 33A along the rear side of thespine 5, through aperture 31 in the spine, through loop 37B of spring35A, and down to the rivet 28. One end of a second adjustment strap 26is connected at 65A to a bottom portion of back pad 49, passes throughslot 33B and is then threaded through friction buckle 33A, forpermitting adjustment and then tightening of the strap 26 in position.The end of strap 26 which is connected to the back pad 49 at 65A isfolded back on itself, and is rivetted for securing the end of the strapto the back pad. The use of a buckle (e.g. LADDER LOCK™) provides easierand finer adjustment of the lumbar spring 13 and upper spring 35A thanis provided with the hook and slot arrangement in the embodiment ofFIGS. 1-6.

Since the lower portion of back pad 49 is secured via strap 26, theretention spring 61 and rivet 63 have been eliminated from thealternative embodiment.

In the alternative embodiment, hook-and-loop fasteners 75A are attacheddirectly to the cross-bar 23, rather than to the foam backrest.

The position adjustment of wire foot 77A is simplified in thealternative embodiment by replacing the two screws 80 (FIGS. 3 and 6),with a single thumb screw 80A which projects into the channel 9 forinsertion into one of the circular apertures 78 in wire foot 77A,thereby locking the wire foot in position.

The plastic foam 79 of the embodiment shown in FIG. 1-6 is replaced inthe alternative embodiment by a rubber sleeve 79A, in a similar manneras discussed above with reference to wire head 81A.

The cross bar 23 is more securely fastened in the alternative embodimentvia a plurality of nuts and bolts (not shown), wherein the bolts areinserted through ten holes 69 extending through the back pad 49 andcorresponding holes through cross bar 23, instead of four holes in theembodiment of FIGS. 1-6.

The screw 47 (FIGS. 4A, 4B and 6) is replaced in the alternativeembodiment by a rivet 47A, while the retention spring 45 is replaced bya flat member 45A having a pair of holes.

In the alternative embodiment, the end 21 of lumbar spring 13 is nolonger bent and the overall shape of the lumbar spring differs from thatin the embodiment of FIGS. 1-6. Furthermore, the method of attaching thelumbar spring 13 to spring member 35A is modified from the embodiment ofFIGS. 1-6, as shown best with reference to FIGS. 9A, 9B and 10.Specifically, the upper end 21 of lumbar spring 13 is inserted throughslot 37A in spring 35A, while the opposite end 15A rests in clip 17A.The clip 17A is secured to the spine 5 via nuts 19B and bolts 19A.

In operation, by pulling downwardly on strap 26, buckle 33A is pulleddownwardly which, in turn, causes strap 25 to pull down spring member35A via loop 37B. This causes the lumbar spring 13 to flex, therebyincreasing the curvature thereof.

Although specific design features are changed in the alternativeembodiment over the embodiment shown in FIGS. 1-6, the general principleof operation remains the same.

In summary, according to the present invention, an adjustable backrestis provided having independent lumbar height and depth adjustment,overall height adjustment to fit different sized patients, mid-backcurve height adjustment, side adjustment to suit each half of apatient's back, upper back side-to-side mobility so that the patient canturn from side-to-side, and a hollow portion just above the base toallow curvature and room so that the backrest of the present inventiondoes not occupy excessive space on the chair. Furthermore, the backrestaccording to the preferred embodiment is portable, and can be affixed tooffice chairs, car seats, wheelchairs, etc, or can be made an integralpart thereof.

Other embodiments and modifications of the invention are contemplated.For example, in a further alternative embodiment the backrest of thepresent invention may be incorporated integrally within a chair, ratherthan being portable as provided in the preferred embodiment. Thisfurther alternative embodiment nonetheless offers all of the advantagesof independent adjustability provided by the preferred embodiment. Thisand all other modifications and embodiments are believed to be withinthe sphere and scope of the invention as defined by the claims appendedhereto.

We claim:
 1. An adjustable backrest for supporting a human backcomprising:a) a spine member; b) a lumbar support member projecting fromsaid spine member; c) a back pad having upper and lower portions, saidupper portion being adapted to support the upper back portion of saidhuman back, and said lower portion resting on said lumbar support memberfor supporting the lumbar portion of said human back, said back padbeing generally triangular with an apex at said upper portion and beingflexible for providing free shoulder rotation and upper back twisting;d) lumbar adjustment means connected to said lumbar support member foradjusting curvature of said lumbar support member relative to said spinemember to accommodate different sizes and shapes of said lumbar portionof said human back; and e) upper back adjustment means connected to saidspine portion intermediate said spine portion and said upper portion ofsaid back pad for adjusting curvature of said upper portion toaccommodate different sizes and shapes of said upper back portion ofsaid human back.
 2. The adjustable backrest of claim 1, furthercomprising length adjustment means connected to said spine member foradjusting the length of said backrest to accommodate different lengthsof said human back.
 3. The adjustable backrest of claim 2, wherein saidlength adjustment means further comprises a foot portion connected to abase portion of said spine member for adjustable sliding movement withrespect thereto.
 4. The adjustable backrest of claim 1, wherein saidlumbar support member further comprises a generally convex springconnected to said spine member.
 5. The adjustable backrest of claim 4,wherein said generally convex spring is connected at one end to saidspine member and secured at an opposite end to a spring member which isconnected to said spine for sliding movement relative thereto.
 6. Theadjustable backrest of claim 5, wherein said lumbar adjustment meansfurther comprises a first adjustment strap connected at one end to saidspine member and at an opposite end to a friction buckle, wherein saidfirst adjustment strap passes upwardly from said buckle along a rearsurface of said spine member, through an aperture in said spine member,through a loop portion of said spring member, and therefrom to saidspine member, and a second adjustment strap connected at one end to abottom portion of said back pad, through a slot in said spine member andtherefrom through said friction buckle, for permitting adjustment andthen tightening of said second adjustment strap in position.
 7. Theadjustable backrest of claim 1, wherein said upper back adjustment meansfurther comprises a cylindrical tube connected to an upper portion ofsaid spine member intermediate said spine member and said upper portionof said back pad, and means for adjusting vertical position of saidcylindrical tube on said spine member to vary the curvature of saidupper portion of said back pad.
 8. The adjustable backrest of claim 1,further comprising a cross bar connected to a central portion of saidlumbar support member, said cross bar having a pair of opposite wingportions extending perpendicular to said spine member.
 9. The adjustablebackrest of claim 8, wherein said back pad is connected to said crossbar for movement therewith.
 10. The adjustable backrest of claim 9,wherein said back pad further includes a pair of individually adjustableside support members and a pair of adjustment straps each connected atone end to respective ones of said wing portions, said pair ofadjustment straps passing through respective apertures in said back pad,and free ends of each of said adjustment straps having hook and loopfastening means being connectable to respective hook and loop typefasteners on an opposite side of said back pad, whereby curvature ofsaid back pad may be adjusted by adjusting the length of said pair ofadjustment straps.
 11. The adjustable backrest of claim 1, wherein saidback pad is covered by resilient foam.
 12. An adjustable backrest forsupporting a human back comprising:a) a spine member having a slidechannel disposed centrally therein; b) an adjustable lumbar supportmember having one end connected to said spine member and an opposite endconnected to said slide channel of said spine member for slidingmovement therein; c) an upper back curvature adjustment member connectedto said slide channel of said spine member for sliding movement therein,said adjustment member being connected to said slide channel at alocation upwardly of said opposite end of said lumbar support member;and d) a back pad having upper and lower portions supported by saidupper back curvature adjustment member and said lumbar support member,respectively, said back pad being generally triangular with an apex atsaid upper portion and being flexible for providing free shoulderrotation and upper back twisting, and wherein independent curvatureadjustment of said upper and lower portions of said back pad is effectedby adjusting the respective positions of said upper back curvatureadjustment member and said opposite end of said lumbar support member,respectively.
 13. The adjustable backrest of claim 12, furthercomprising an upper back support spring intermediate said upper portionof said back pad and said upper back curvature adjustment member. 14.The adjustable backrest of claim 12, wherein said lumbar support memberis a leaf spring.
 15. The adjustable backrest of claim 12, wherein saidupper back curvature adjustment member is a horizontally disposedcylinder.
 16. The adjustable backrest of claim 12, further including anextension from a lower portion of said spine member for adjusting theeffective length of said backrest.
 17. An adjustable backrest forsupporting a human back comprising:a) a spine member; b) a lumbarsupport member projecting from said spine member; c) a back pad havingupper and lower portions, said upper portion being adapted to supportthe upper back portion of said human back, and said lower portionresting on said lumbar support member for supporting the lumbar portionof said human back, said back pad being generally triangular with anapex at said upper portion and being flexible for providing freeshoulder rotation and upper back twisting; d) lumbar adjustment meansconnected to said lumbar support member for adjusting curvature of saidlumbar support member relative to said spine member to accommodatedifferent sizes and shapes of said lumbar portion of said human back; e)upper back adjustment means connected to said spine portion intermediatesaid spine portion and said upper portion of said back pad for adjustingcurvature of said upper portion to accommodate different sizes andshapes of said upper back portion of said human back; and f) lengthadjustment means connected to said spine member for adjusting the lengthof said backrest to accommodate different lengths of said human back.18. The adjustable backrest of claim 17, wherein said length adjustmentmeans further comprises a foot portion connected to a base portion ofsaid spine member for adjustable sliding movement with respect thereto.19. The adjustable backrest of claim 17, wherein said back pad iscovered by resilient foam.
 20. An adjustable backrest for supporting ahuman back comprising:a) a spine member; b) a lumbar support memberprojecting from said spine member, said lumbar support member furthercomprising a generally convex spring connected to said spine member; c)a back pad having upper and lower portions, said upper portion beingadapted to support the upper back portion of said human back, and saidlower portion resting on said lumbar support member for supporting thelumbar portion of said human back, said back pad being generallytriangular with an apex at said upper portion and being flexible forproviding free shoulder rotation and upper back twisting; d) lumbaradjustment means connected to said lumbar support member for adjustingcurvature of said lumbar support member relative to said spine member toaccommodate different sizes and shapes of said lumbar portion of saidhuman back; and e) upper back adjustment means connected to said spineportion intermediate said spine portion and said upper portion of saidback pad for adjusting curvature of said upper portion to accommodatedifferent sizes and shapes of said upper back portion of said humanback.
 21. The adjustable backrest of claim 20, wherein said generallyconvex spring is connected at one end to said spine member and securedat an opposite end to a spring member which is connected to said spinefor sliding movement relative thereto.
 22. The adjustable backrest ofclaim 21, wherein said lumbar adjustment means further comprises a firstadjustment strap connected at one end to said spine member and at anopposite end to a friction buckle, wherein said first adjustment strappasses upwardly from said buckle along a rear surface of said spinemember, through an aperture in said spine member, through a loop portionof said spring member, and therefrom to said spine member, and a secondadjustment strap connected at one end to a bottom portion of said backpad, through a slot in said spine member and therefrom through saidfriction buckle, for permitting adjustment and then tightening of saidsecond adjustment strap in position.
 23. The adjustable backrest ofclaim 20, wherein said back pad is covered by resilient foam.
 24. Anadjustable backrest for supporting a human back comprising:a ) a spinemember; b) a lumbar support member projecting from said spine member; c)a back pad having upper and lower portions, said upper portion beingadapted to support the upper back portion of said human back, and saidlower portion resting on said lumbar support member for supporting thelumbar portion of said human back, said back pad being generallytriangular with an apex at said upper portion and being flexible forproviding free shoulder rotation and upper back twisting; d) lumbaradjustment means connected to said lumbar support member for adjustingcurvature of said lumbar support member relative to said spine member toaccommodate different sizes and shapes of said lumbar portion of saidhuman back; and e) upper back adjustment means connected to said spineportion intermediate said spine portion and said upper portion of saidback pad for adjusting curvature of said upper portion to accommodatedifferent sizes and shapes of said upper back portions of said humanback, and wherein said upper back adjustment means further comprises acylindrical tube connected to an upper portion of said spine memberintermediate said spine member and said upper portion of said back pad,and means for adjusting vertical position of said cylindrical tube onsaid spine member to vary the curvature of said upper portion of saidback pad.
 25. The adjustable backrest of claim 24, wherein said back padis covered by resilient foam.
 26. An adjustable backrest for supportinga human back comprising:a) a spine member; b) a lumbar support memberprojecting from said spine member; c) a back pad having upper and lowerportions, said upper portion being adapted to support the upper backportion of said human back, and said lower portion resting on saidlumbar support member for supporting the lumbar portion of said humanback, said back pad being generally triangular with an apex at saidupper portion and flexible for providing free shoulder rotation andupper back twisting; d) lumbar adjustment means connected to said lumbarsupport member for adjusting curvature of said lumbar support memberrelative to said spine member to accommodate different sizes and shapesof said lumbar portion of said human back; e) upper back adjustmentmeans connected to said spine portion intermediate said spine portionand said upper portion of said back pad for adjusting curvature of saidupper portion to accommodate different sizes and shapes of said upperback portions of said human back; f) a cross bar connected to a centralportion of said lumbar support member; and g) back pad adjustment meansconnected to said cross bar and said back pad for providing side-to-sidecontour adjustment of said back pad to accommodate different lateralsizes and shapes of said human back.
 27. The adjustable backrest ofclaim 26, wherein said cross bar further comprises a pair of oppositewing portions extending perpendicular to said spine member.
 28. Theadjustable backrest of claim 27, wherein said back pad adjustment meansfurther includes a pair of adjustment straps each connected at one endto respective ones of said wing portions, said pair of adjustment strapspassing through respective apertures in said back pad, and free ends ofeach of said adjustment straps having hook and loop fastening meansbeing connectable to respective hook and loop type fasteners on anopposite side of said back pad, whereby the contour of said back pad maybe adjusted by adjusting the length of said pair of adjustment straps.29. The adjustable backrest of claim 26, wherein said back pad iscovered by resilient foam.
 30. An adjustable backrest for supporting ahuman back comprising:a) a spine member having a slide channel disposedcentrally therein; b) an adjustable lumbar support member having one endconnected to said spine member and an opposite end connected to saidslide channel of said spine member for sliding movement therein; c) anupper back curvature adjustment member connected to said slide channelof said spine member for sliding movement therein, said adjustmentmember being connected to said slide channel at a location upwardly ofsaid opposite end of said lumbar support member; d) a back pad havingupper and lower portions supported by said upper back curvatureadjustment member and said lumbar support member, respectively, andwherein independent curvature adjustment of said upper and lowerportions of said back pad is effected by adjusting the respectivepositions of said upper back curvature adjustment member and saidopposite end of said lumbar support member, respectively; and e) anupper back support spring intermediate said upper portion of said backpad and said upper back curvature adjustment member.
 31. An adjustablebackrest for supporting a human back comprising:a) a spine member havinga slide channel disposed centrally therein; b) an adjustable lumbarsupport member having one end connected to said spine member and anopposite end connected to said slide channel of said spine member forsliding movement therein, and wherein said lumbar support member is aleaf spring; c) an upper back curvature adjustment member connected tosaid slide channel of said spine member for sliding movement therein,said adjustment member being connected to said slide channel at alocation upwardly of said opposite end of said lumbar support member;and d) a back pad having upper and lower portions supported by saidupper back curvature adjustment member and said lumbar support member,respectively, and wherein independent curvature adjustment of said upperand lower portions of said back pad is effected by adjusting therespective positions of said upper back curvature adjustment member andsaid opposite end of said lumbar support member, respectively.
 32. Anadjustable backrest for supporting a human back comprising:a) a spinemember having a slide channel disposed centrally therein; b) anadjustable lumbar support member having one end connected to said spinemember and an opposite end connected to said slide channel of said spinemember for sliding movement therein; c) an upper back curvatureadjustment member connected to said slide channel of said spine memberfor sliding movement therein, said adjustment member being connected tosaid slide channel at a location upwardly of said opposite end of saidlumbar support member, and wherein said upper back curvature adjustmentmember is a horizontally disposed cylinder; and d) a back pad havingupper and lower portions supported by said upper back curvatureadjustment member and said lumbar support member, respectively, andwherein independent curvature adjustment of said upper and lowerportions of said back pad is effected by adjusting the respectivepositions of said upper back curvature adjustment member and saidopposite end of said lumbar support member, respectively.
 33. Anadjustable backrest for supporting a human back comprising:a) a spinemember having a slide channel disposed centrally therein; b) anadjustable lumbar support member having one end connected to said spinemember and an opposite end connected to said slide channel of said spinemember for sliding movement therein; c) an upper back curvatureadjustment member connected to said slide channel of said spine memberfor sliding movement therein, said adjustment member being connected tosaid slide channel at a location upwardly of said opposite end of saidlumbar support member; d) a back pad having upper and lower portionssupported by said upper back curvature adjustment member and said lumbarsupport member, respectively, and wherein independent curvatureadjustment of said upper and lower portions of said back pad is effectedby adjusting the respective positions of said upper back curvatureadjustment member and said opposite end of said lumbar support member,respectively; and e) an extension from a lower portion of said spinemember for adjusting the effective length of said backrest.